Uplink Power Control

ABSTRACT

An uplink power control that is applied to a user equipment ( 300 ) when in communication with a serving radio base station ( 10 ) and at least one other radio base station ( 20 ) involves generating a quality representation of an uplink control channel ( 12 ) from the user equipment ( 300 ) to the serving radio base station ( 10 ). The quality representation is compared to a threshold value and this comparison defines a selective processing of transmit power control commands received by the user equipment ( 300 ) from the serving and/or non-serving radio base stations ( 10, 20 ).

TECHNICAL FIELD

The present embodiments generally relate to uplink power control in acommunication network and, more particularly, to such a power controlwhen a user equipment is connected to multiple radio base stations inthe communication network.

BACKGROUND

One characteristics of Wideband Code Division Multiple Access/High SpeedPacket Access (WCDMA/HSPA) is that downlink transmission to a specificuser equipment is only performed by one radio base station, referred toas the serving radio base station. Evidently it is only the servingradio base station that benefits from knowledge of the physical layerinformation (Hybrid Automatic Repeat reQuest (HARQ) acknowledgements andChannel Quality Information/Pre-Coding Information (CQI/PCI))transmitted on the High Speed Dedicated Physical Control Channel(HS-DPCCH) by the user equipment and thus only the serving radio basestation decodes the HS-DPCCH.

Uplink data transmission from a user equipment can, in WCDMA/HSPA, onthe other hand be received by multiple radio base stations. The set ofradio base stations that decode the data transmissions from a particularuser equipment constitute the active set for that user equipment. Someof the uplink related control channels are transmitted by all radio basestations in the active set, while some other control channels aretransmitted by the serving radio base station only. One of the controlchannels transmitted by all radio base stations in the active set is theFractional Dedicated Physical Channel (F-DPCH), which is used to controlthe transmit power of the user equipment. More specifically, transmitpower control (TPC) commands sent on the F-DPCH adjust the DedicatedPhysical Control Channel (DPCCH) transmit power of the user equipment.

The DPCCH transmit power is used as reference for all other physicalchannels transmitted by the user equipment. The power ratio betweendifferent physical channels is constant, which means that a change inthe DPCCH transmit power will result in that the transmit power of allother physical channels is also changed.

For a user equipment in soft handover (SHO) the transmit power on theuplink will be controlled by the radio base station associated with thehighest Signal-to-Interference Ratio (SIR). FIGS. 2A and 2Bschematically illustrate two examples of situations where a non-servingradio base station 20 would control the uplink power of the userequipment 300: 1) if the measured uplink interference level at theserving radio base station 10 is higher than the one measured by thenon-serving radio base station 20 (FIG. 2A); and 2) if the pilot (DPCCH)power of the downlink is lower in the non-serving radio base station 20than in the serving radio base station 10 (FIG. 2B). The latter can be aresult of that the uplink link budget towards the non-serving radio basestations 20 is stronger than the link budget towards the serving radiobase station 10.

In FIG. 2A, the interference level originating from another userequipment 30 can result in that the SIR target is only met by thenon-serving radio base station 20. In FIG. 2B, the user equipment 300will be power controlled by the non-serving radio base station 20 whenthe Common Pilot Channel (CPICH) power is lower for the non-servingradio base station 20 than for the serving radio base station 10 due todownlink power asymmetry and the fact that the serving cell is based ondownlink measurements. In both these cases the transmit power of theuser equipment 300 is adjusted so that the quality at the non-servingradio base station 20 meets the desired target.

A consequence when the non-serving radio base station is controlling theuplink power is that the HS-DPCCH at the serving radio base station maybecome so weak that it cannot be correctly decoded or even detected.This can be a consequence of i) the received HS-DPCCH power at theserving base station is too weak and/or ii) DPCCH quality at the servingradio base station is so weak so that an adequate channel estimatecannot be derived at the serving radio base station.

The HS-DPCCH carries the HARQ acknowledgement and CQI/PCI related to thedownlink transmission of the user equipment. This information is used bythe serving radio base station to decide how much information totransmit in a given Transmission Time Interval (TTI) and to decidewhether a packet needs to be retransmitted. Inferior HS-DPCCH qualitycan thus result in that:

-   -   The HARQ acknowledgements, indicating whether the user equipment        was able to decode transmitted downlink transport blocks, are        not detected or erroneously decoded. This will result in        unnecessary layer 1 (L1) as well as Radio Link Control (RLC)        retransmission.    -   The accuracy and availability of the CQI/PCI is reduced.

Hence there are good reasons for ensuring a sufficient HS-DPCCH qualityat the serving radio base station.

To combat these effects in existing solutions the HS-DPCCH typically hasa higher power offset in SHO than in non-SHO situations.

On top of this the network has the possibility to order the userequipment to always repeat the HARQ Acknowledgements/Negativeacknowledgements (ACK/NACKs) on the HS-DPCCH. The drawback with thissolution is however a reduction in the achievable downlink bit ratesince a HARQ-ACK/NACK repetition factor of x results in that the networkcan only schedule packet transmissions to the user equipment once everyx:th TTI.

There is therefore a need for an efficient power control solution thatcan be applied to ensure the HS-DPCCH quality when a user equipment hasmore than one radio base station in its active set.

WO 2009/072945 describes a method and an arrangement of obtainingefficient power control during soft handover in a communication networksystem when a user equipment is in communication with two or more radiobase stations over a radio interface on downlink and uplink channels.TPC commands are received from the two or more radio base stations onthe downlink channels. The received TPC commands are analyzed and apower offset on the uplink channels is adjusted based on the analyzedTPC commands. This technique does not ensure that the DPCCH qualityneeded for channel estimation at the serving radio base station issufficient.

SUMMARY

It is a general objective to provide an efficient power control for auser equipment.

It is a particular objective to provide such a power control of anuplink control channel of the user equipment.

An aspect of the embodiments defines a power control method in acommunication network when a user equipment is in communication with aserving radio base station and at least one other radio base stationover a radio interface on uplink channels. The method comprisesgenerating a quality representation at the user equipment of an uplinkcontrol channel from the user equipment to the serving radio basestation. The user equipment compares this quality representation to athreshold value. This comparison defines a selective processing by theuser equipment of transmit power control commands received from theserving and/or non-serving radio base station.

Another aspect of the embodiments defines a user equipment comprising arepresentation generator configured to generate a quality representationof an uplink control channel from the user equipment to a serving radiobase station in a communication network. A comparator of the userequipment is configured to compare the quality representation to athreshold value. The user equipment also comprises a processorconfigured to perform a selective processing of transmit power controlcommands based on the comparison of the quality representation to thethreshold value. These transmit power control commands are received by areceiver of the user equipment from the serving radio base stationand/or from at least one other radio base station of the communicationnetwork.

A further aspect of the embodiments defines a computer program for powercontrol in a communication network when a user equipment is incommunication with a serving radio base station and at least one otherradio base station over a radio interface on uplink channels. Thecomputer program comprises code means which when run by a processingunit of the user equipment causes the processing unit to generate aquality representation of an uplink control channel from the userequipment to the serving radio base station. The processing unit is alsocaused to compare the quality representation to a threshold value andperform, based on this comparison, a selective processing of transmitcontrol commands received from the serving and/or non-serving radio basestation.

Yet another aspect of the embodiments defines a computer program productcomprising computer readable code means and a computer program accordingto above stored on the computer readable code means.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with further objects and advantages thereof, maybest be understood by making reference to the following descriptiontaken together with the accompanying drawings, in which:

FIG. 1 is a schematic illustration of a communication network accordingto an embodiment;

FIGS. 2A and 2B illustrate communication networks with a user equipmentduring soft handover;

FIG. 3 is a flow chart showing a power control method according to anembodiment;

FIG. 4 is a flow chart showing a particular embodiment of the generatingstep in FIG. 3;

FIG. 5 is a flow chart showing another particular embodiment of thegenerating step in FIG. 3;

FIG. 6 is a flow chart showing a particular embodiment of the processingstep in FIG. 3;

FIG. 7 is a block diagram of a user equipment according to anembodiment;

FIG. 8 is a block diagram of an embodiment of the representationgenerator in FIG. 7;

FIG. 9 is a block diagram of another embodiment of the representationgenerator in FIG. 7; and

FIG. 10 is a block diagram of a user equipment according to anotherembodiment.

DETAILED DESCRIPTION

The present embodiments generally relate to uplink power control in acommunication network and, more particularly, to such a power controlwhen a user equipment is connected to multiple radio base stations inthe communication network.

FIG. 1 is a schematic overview of a portion of a communication network 1to which the present embodiments can be applied. The communicationnetwork 1 is preferably a wireless, radio-based communication network orsystem providing communication services to connected user equipment 300.In particular, the communication network 1 comprises multiple radio basestations 10, 20, also referred to as Node-B or base stations in the art.Each such radio base station 10, 20 provides communication serviceswithin a coverage area, typically denoted cell. The radio base stations10, 20 are in turn connected to and controlled by a control network node40, denoted Radio Network Controller (RNC) 40 in the art.

According to the embodiments, the user equipment 300 is in communicationwith multiple radio base stations 10, 20 over the radio interface. Oneof these radio base stations 10, 20 is then the so-called serving radiobase station 10, whereas the at least one other radio base station 20 isdenoted non-serving radio base station 20. Generally, downlinktransmissions of user-specific data is typically only performed by theserving radio base station 10 on a downlink channel 14 towards the userequipment 300. However, uplink data transmissions from the userequipment 300 can on the contrary be received by not only the servingradio base station 10 but also by the at least one other radio basestation 20. These uplink data transmissions are schematicallyillustrated by channels 12, 22 in FIG. 1. The serving radio base station10 and the at least one other radio base station 20 form the so calledactive set of the user equipment 300. All radio base stations 10, 20 inthe active set transmit some of the uplink related control channels asindicated in the background and schematically illustrated by thechannels 14, 24 in FIG. 1.

As indicated in the background section, in a communication network 1with a user equipment 300 having an active set of multiple radio basestations 10, 20, the uplink power of the user equipment 300 could becontrolled by a non-serving radio base station 20. FIGS. 2A and 2Billustrate such cases in connection with a user equipment 300 duringsoft handover (SHO). In FIG. 2B, the user equipment 300 will bepower-controlled by the non-serving radio base station 20 when GB>GA,wherein the Common Pilot Channel (CPICH) power of the serving radio basestation 10 is GAPCPICH, A and the CPICH power of the non-serving radiobase station 20 is G_(B)P_(CPICH, B), where G_(A,B) denotes respectivepath gain values. In this case, the transmit power of the user equipment300 is adjusted so that the quality at the non-serving radio basestation 20 meets its defined target. This situation is common ifP_(CPICH, B)<P_(CPICH, A). In FIG. 2A the interference levels in the twocells can result in that the Signal-to-Interference (SIR) target is onlymet by the non-serving radio base station 20. As a consequence, thetransmit power of the user equipment 300 can be set by the non-servingradio base station 20 so that some of the uplink control channels aretoo weak and cannot be correctly decoded or even detected at the servingradio base station 10. In both figures, the SHO area is indicated by SHOand in FIG. 2B the point of serving cell change is indicated by anarrow.

Hence, there is today a problem within communication networks where auser equipment can be in communication with multiple radio base stationsin terms of a power control of the user equipment performed by anon-serving radio base station. These problems are expected to becomeeven worse in the future. Today, existing network deployments areusually based on macro radio base stations. All these macro radio basestations typically use similar transmission power. Moreover,traditionally user equipments are not designed to apply multi-antennatechniques in the uplink and the user equipment is typically scheduledin code division multiplexing (CDM) fashion.

Multi-antenna transmission techniques for the uplink enable beam formingso that the user equipment pre-codes the signals so that these addcoherently at a receiver. Another way to interpret beam forming is thatthe pre-coding vector applied at the user equipment creates a beamtowards a particular radio base station. This means that the pre-codingwill increase the link asymmetry, e.g. if the beam is directed towardsthe non-serving radio base station. Hence, the previously discussedproblems will become even worse with multi-antenna uplink transmission.

Today there is a trend to complement traditional macro radio basestations with micro and/or pico radio base stations. Such micro and picoradio base stations use less transmission power as compared to macroradio base stations. In order to benefit from micro and pico radio basestations in the downlink it is therefore desirable that serving radiobase station (or cell) changes are based on E_(C)/I₀ (ratio of receivedenergy per chip and the interference level) measurements. This will,however, result in that the cell border is moved towards the non-servingradio base station. The previously discussed problems will thereforebecome even worse with the introduction of micro and/or pico radio basestations.

In order to reduce intra-cell interference the serving radio basestation can chose to time multiplex the transmission of two or more userequipments. Assuming that the interference from other cells(I_(OtherCell)) is constant, the SIR can be approximated for a userequipment by:

${SIR}_{DPCCH} = \frac{P_{DPCCH}}{I_{Self} + I_{OtherCell} + P_{n}}$when  the  user  equipment  is  scheduled  and:${SIR}_{DPCCH} = \frac{P_{DPCCH}}{I_{OwnCell} + I_{OtherCell} + P_{n}}$

when another user equipment is scheduled, wherein P_(DPCCH) denotes thetransmit power of the Dedicated Physical Control Channel (DPCCH) andP_(n) denotes the power of the noise. By noting that the own cellinterference from other users (I_(OwnCell)) is typically greater thanthe self-interference due to multi-path fading (I_(Self)), it is clearthat the SIR will be significantly lower when a user equipment is notscheduled compared to when the user equipment is scheduled. Hence, theSIR will vary significantly depending on whether the user equipment isscheduled or not in a certain time slot.

Thus, it becomes evident from above that the shortcomings of the priorart techniques will suffer even more in the near future. Hence, there isa need for a more efficient power control solution than the prior artsolution of merely switching to a higher power offset for a userequipment in SHO. The present embodiments provide such a more efficientsolution to the power control problems that can arise when a userequipment is in communication with both a serving radio base station andat least one other radio base station.

FIG. 3 is a flow chart illustrating a power control method according toan embodiment. The present power control method is applied when a userequipment is in communication with a serving radio base station and atleast one other radio base station, i.e. has at least two radio basestations in its active set. An example of such a situation is duringSHO. The embodiments are, however, not limited thereto. Also othersituations where the user equipment has uplink channels to multipleradio base stations are possible and within the scope of theembodiments. An example of such another situation is when radio basestations transmit multiple downlink streams of data to a user equipment.

The method generally starts in step S1 where the user equipmentgenerates a quality representation of or for an uplink (UL) controlchannel from the user equipment to the serving radio base station. Thisgenerated quality representation, hence, reflects and is indicative ofthe quality of the particular UL control channel to the serving radiobase station. In a next step S2, the user equipment compares the qualityrepresentation generated in step S1 with a threshold value. The resultof this comparison, i.e. whether the quality representation indicates aquality above or below a threshold quality defined by the thresholdvalue, is employed in the processing of step S3. In this step S3 theuser equipment performs a selective processing of transmit power control(TPC) commands received from at least one of its connected radio basestations. Thus, the user equipment performs the selective processing ofthe received TPC commands based on the comparison of the qualityrepresentation to the threshold value as performed in step S2.

Selective processing refers herein to that the particular way that theuser equipment processes and uses the received TPC commands depends onthe outcome of the comparison between the quality representation and thethreshold value. Hence, if the quality representation exceeds thethreshold value the user equipment performs a first type of processingof received TPC commands, whereas the user equipment instead performs asecond, different processing of received TPC commands if the qualityrepresentation would have been below the threshold value.

The method then ends. In a particular embodiment, which is furtherdescribed herein, the user equipment periodically or intermittentlygenerates a new or updated quality representation to reflect the currentquality situation for the UL control channel. Hence, the method steps S1to S3 are preferably repeated several times for the user equipment aslong as it is in communication with multiple radio base stations in thecommunication network.

The UL control channel for which a quality representation is generatedin step S1 is preferably a control channel that is used by the userequipment for transmitting downlink feedback information to the servingradio base station. In particular, the control channel is preferablyused by the user equipment for transmitting Hybrid Automatic Repeatrequest (HARQ) acknowledgements/non-acknowledgements (ACKs/NACKs) and/orChannel Quality Information/Pre-Coding Information (CQI/PQI) to theserving radio base station. A preferred implementation embodiment thatis adapted to a communication network employing Wideband Code DivisionMultiple Access/High Speed Packet Access (WCDMA/HSPA) is when the ULcontrol channel is a High Speed Dedicated Physical Control Channel(HS-DPCCH).

TPC commands are generally transmitted on UL related control channelsthat are sent by the serving radio base station and the at least oneother radio base station. In a particular embodiment, this UL relatedcontrol channel is the previously mentioned Fractional DedicatedPhysical Channel (F-DPCH) that are sent by all radio base stations inthe active set for the user equipment. TPC is a general technique usedto prevent too much unwanted interference between different transmittersand receivers in a communication network. The idea of using TPC is toautomatically reduce the used transmission power of a user equipment tothereby reduce any interference problems and in addition achieve anincreased battery capacity of the user equipment.

In the following various implementation embodiments of the power controlmethod will be further described.

The quality representation generated in step S1 of FIG. 3 by the userequipment can be any representation of the quality of the UL controlchannel, preferably in the form of a HS-DPCCH quality representation orestimate.

In an embodiment, the user equipment compares the HARQ ACK messages ithas transmitted on the HS-DPCCH (UL control channel) to the servingradio base station with the packet transmission that it receives on adownlink channel from the serving radio base station. Thus, if the userequipment previously has successfully received a packet on the downlinkchannel, transmitted an HARQ ACK on the HS-DPCCH to the serving radiobase station with regard to that packet but anyway receives aretransmission of the same packet and/or an increased redundancy versionthen this is an indicator of that the HS-DPCCH quality at the servingradio base station is inferior. Hence, in this embodiment the userequipment generates the quality representation based on a comparison oftransmission acknowledgement messages transmitted on the UL controlchannel with packet transmissions received on a downlink data channelfrom the serving radio base station.

In another embodiment, the user equipment monitors for TPC commandsreceived on the F-DPCH from the serving radio base station and generatesthe quality representation based on these received TPC commands. Thus,if the user equipment detects a significant amount of TPC UP commandsfrom the serving radio base station during a defined time period, thisis an indicator of that the HS-DPCCH quality is inferior and that theuser equipment could be power controlled by a non-serving radio basestation. Hence, in this embodiment the user equipment generates thequality representation based on monitoring of TPC commands transmittedfrom the serving radio base station to the user equipment. The qualityrepresentation could then be an indication of the percentage of the TPCcommands that, during a defined time period or for a defined number ofTPC commands, indicate an increase in transmit power of the userequipment. An alternative but related approach is to determine thequality representation based on the percentage of the TPC commands fromthe serving radio base station that indicate a decrease in transmitpower of the user equipment, i.e. so called TPC DOWN commands.

A further embodiment is to estimate the difference in downlink (DL) pathloss between the serving radio base station and the at least non-servingradio base station. Such a downlink path loss based procedure can beperformed based on path loss estimations of a respective pilot channel,such as CPICH, from the radio base stations in the active set. The pathlosses represent the reduction in power density or attenuation of thesignals transmitted from the radio base stations towards the userequipment. The path loss may be due to various effects, such asfree-space loss, refraction, diffraction, reflection and absorption. Thepath losses can be estimated or predicted by the user equipmentaccording to methods well known in the art, such as statistical orstochastic methods or deterministic methods. Thus, in this embodimentthe user equipment generates the quality representation based onestimation of the difference in downlink path loss between the servingradio base station and the at least one other radio base station.

In another embodiment, the user equipment generates the qualityrepresentation based on a combination of at least two of the abovepresented embodiments. Thus, in such a case the quality representationis determined based on at least two of the techniques disclosed in theforegoing and relating to i) comparing transmitted HARQ ACK/NACKmessages with received data packets, ii) monitoring TPC commands fromthe serving radio base station, and iii) estimation of DL path lossdifference.

FIG. 4 is a flow chart illustrating an embodiment of the generating stepS1 in FIG. 3. In this embodiment, the user equipment determines multiplequality estimates for the UL control channel, preferably HS-DPCCH, atdifferent time instances in step S11. In such a case, the user equipmentcan be configured to perform this step S11 over a predefined period oftime to thereby determine the quality estimates during this period oftime. In an alternative approach, the user equipment is configured todetermine a predefined number of quality estimates. The qualityestimates determined in step S11 are obtained according to any of thepreviously described embodiments. Thus, the user equipment then hasaccess to multiple quality estimates reflecting the quality of the ULcontrol channel at multiple different time instances: Q_(HS-DPCCH) (t),Q_(HS-DPCCH)(t−1), . . . , Q_(HS-DPCCH)(t−M), M≧1. These multipledifferent time instances are then co-processed in order to calculate thequality representation based on these multiple quality estimates. Hence,the quality representation is in this embodiment a function of themultiplequality estimates, i.e. ƒ(Q_(HS-DPCCH)(t), Q_(HS-DPCCH)(t−1), .. . , Q_(HS-DPCCH)(t−M)).

FIG. 4 illustrates a particular example of a function that can be usedaccording to the embodiments to calculate the quality representation. Inthis embodiment, the quality representation is calculated as an averageof the multiple quality estimates determined in step S11. Hence, thequality representation is thereby calculated as

$\frac{{Q_{{HS}\text{-}{DPCCH}}(t)},{Q_{{HS}\text{-}{DPCCH}}\left( {t - 1} \right)},\ldots \mspace{14mu},{Q_{{HS}\text{-}{DPCCH}}\left( {t - M} \right)}}{M + 1}$

in step S12. Thus, in this embodiment the quality representationreflects an average quality situation for the UL control channel,preferably HS-DPCCH, during the time for which the quality estimateshave been determined in step S11.

In another but related embodiment, the function ƒ( ) does not output theaverage of the multiple quality estimates but rather the median of themultiple quality estimates. Also this embodiment will calculate aquality representation that reflects an average quality situation forthe UL control channel, preferably HS-DPCCH.

The method then continues from step S12 to step S2 of FIG. 3, where thecalculated quality representation is compared to the threshold.

FIG. 5 is a flow chart illustrating another embodiment of the generatingstep S1 in FIG. 3. The method starts in step S21 where the userequipment determines multiple quality estimates for the UL controlchannel, preferably HS-DPCCH. This step S21 basically corresponds tostep S11 of FIG. 4 and is therefore not further discussed herein. Inthis embodiment another function ƒ( ) than calculating an average ormedian of the quality estimates is used in step S22 to get the qualityrepresentation. Thus, step S22 selects the maximum quality estimateamong the quality estimates determined in step S21 and uses thisselected quality estimate as the quality representation for the ULcontrol channel, preferably HS-DPCCH. Thus, thequality representation ismax(Q_(HS-DPCCH)(t), Q_(HS-DPCCH) (t−1), . . . , Q_(HS-DPCCH)(t−M)).Hence, in this embodiment the user equipment investigates whether thequality for the UL control channel, preferably HS-DPCCH, lies below thequality represented by the threshold value for the time period duringwhich the quality estimates are determined. Such a situation thenindicates a poor HS-DPCCH quality. The method then continues to step S2of FIG. 3.

In an alternative embodiment, the function ƒ( ) instead selects theminimum quality estimate among the multiple quality estimates. Hence,the quality representation is min(Q_(HS-DPCCH)(t), Q_(HS-DPCCH)(t−1), .. . , Q_(HS-DPCCH)(t−M)). This embodiment is particularly suitable for asituation with too excessive quality of the HS-DPCCH.

Step S2 of FIG. 3 then compares the quality representation, such ascalculated in step S12 of FIG. 4 or S22 of FIG. 5, with the thresholdvalue. Thus, the user equipment then investigates whetherƒ(Q_(HS-DPCCH)(t), Q_(HS-DPCCH)(t−1), . . . , Q_(HS-DPCCH)(t−M))<Q₁,where Q₁ represents the threshold value. In this embodiment, a low valueof the quality representation indicates a poor quality of the UL controlchannel, preferably HS-DPCCH. Hence, if the quality representation isbelow the threshold value this indicates such a poor channel quality andthat it is likely that the user equipment will be power controlled by anon-serving radio base station. In an alternative approach, a highquality representation could indicate a poor quality of the UL controlchannel. In such a case, step S2 preferably investigates whether thequality representation exceeds the threshold value. This would thenindicate a poor channel quality and a high probability that the userequipment is power controlled by a non-serving radio base station.

Hence, step S1 of FIG. 3 preferably investigates whether the quality ofthe UL control channel, preferably HS-DPCCH, as indicated by the qualityrepresentation, is poorer or worse than a threshold quality, asrepresented by the threshold value. In such a case, the user equipmentshould in step S3 perform a processing of the received TPC commands thatis selected to combat the poor channel quality.

FIG. 6 is a flow diagram illustrating an embodiment of this processingstep S3 in FIG. 3 in a situation with poor channel quality. The methodcontinues from step S2 where the comparison between the qualityrepresentation and the threshold value indicates the poor qualitysituation for the relevant UL control channel, preferably HS-DPCCH. Instep S31 the user equipment is thereby configured to neglect a selectedfraction of received TPC commands that are intended to trigger adecrease in the transmit power of the UL control channel. In thissituation the user equipment is typically power controlled by anon-serving radio base station. Hence, any TPC DOWN commands received bythe user equipment are typically transmitted by the non-serving radiobase station. If the user equipment would have reduced its transmitpower even further based on these received TPC commands, the transmitpower of the relevant UL control channel, preferably HS-DPCCH and DPCCH(which is used for channel estimation), would be even lower and theproblems previously discussed herein would be aggravated.

Hence, in a particular embodiment the user equipment thereby ignores orneglects at least one of the received TPC commands indicating that theuser equipment should reduce its transmit power. Neglecting a TPCcommand refers herein to that the user equipment does not decrease itstransmit power on the physical channels even though it has received aTPC command that instructs the user equipment to make such a transmitpower reduction.

As previously discussed herein, the TPC commands are preferably receivedon the F-DPCH from the radio base stations in the active set. Such a TPCcommand then urges the user equipment to modify, i.e. increase ordecrease, its DPCCH transmit power (P_(DPCCH)). The transmit power ofthe relevant UL control channel, i.e. preferably HS-DPCCHP(P_(HS-DPCCH)), will then correspondingly be modified through therelation between the DPCCH transmit power and the HS-DPCCH transmitpower:

${P_{{HS}\text{-}{DPCCH}} = {\left( \frac{\beta_{hs}}{\beta_{c}} \right)^{2} \times P_{DPCCH}}},$

wherein β_(hs) and β_(c) are semi-static quantized amplitude ratios thatare signaled by the radio network controller.

In an embodiment, the user equipment could be configured to neglect allTPC DOWN commands that are received from non-serving radio base stationsin step S31 if the quality representation indicates a poor quality ofthe UL control channel in the comparison with the threshold value. Insuch a case, the user equipment will not further reduce the transmitpower until the quality representation indicates that the quality of therelevant UL control channel is high enough so that the serving radiobase station can efficiently receive any messages transmitted thereon bythe user equipment. At this point it is likely that the user equipmentwill no longer be power controlled by a non-serving radio base stationbut instead by the serving radio base station. Hence, the user equipmentcan then process any received TPC commands as normal, i.e. increase ordecrease its transmit power depending on whether it receives any TPC UPor DOWN commands.

In another embodiment, the user equipment is configured to neglect aselected sub-fraction of the received TPC DOWN commands, preferably suchTPC DOWN commands received from a non-serving radio base station. Forinstance, the user equipment could be configured to neglect everysecond, every third or every fourth received TPC DOWN command. This thenimplies that any reduction in transmit power of the user equipment willbe performed at a much slower pace as compared to processing each TPCDOWN command.

A further embodiment is to select the fraction of TPC DOWN commands toignore based on the quality representation generated for the relevant ULcontrol channel. Thus, if the quality representation indicates a verypoor channel quality, for instance, every TPC DOWN command could beneglected by the user equipment. However, if the quality representationinstead indicates only a slightly poor channel quality, for instance,every y^(th) TPC DOWN command is ignored, where y is a predefined fixedinteger number equal to or larger than two or is determined based on thequality representation. This latter embodiment can be realized by havingaccess to multiple different threshold values in the comparison of stepS2 in FIG. 3. If the quality representation then indicates a really poorchannel quality and is below a first threshold Q₁ every TPC DOWN commandis ignored. If the quality representation instead is larger than thefirst threshold Q₁ but smaller than a second threshold Q₂ (Q₂>Q₁) then,for instance, every second TPC DOWN command is ignored and so on.

Thus, in these particular embodiments the selected fraction of TPCcommands to neglect by the user equipment in step S31 is determinedbased on the quality representation.

Alternatively, or in addition, the fraction of TPC DOWN commands thatshould be neglected could be determined as a function of, i.e. bedependent on, the path loss difference between the user equipment andthe serving radio base station and the user equipment and thenon-serving radio base station(s). Alternatively, or in addition, thefraction could be signaled to the user equipment via Radio ResourceControl (RRC) signaling.

In clear contrast, if the channel quality of the UL control channel issufficient as indicated by the comparison between the qualityrepresentation and the threshold value, the selective processing in stepS3 preferably involves that the user equipment adjusts its transmitpower of the UL control channel in response to and based on received TPCUP or DOWN commands. Hence, in such a case the received TPC commands arenot neglected by the user equipment.

The method of the embodiments is particularly advantageous if thenetwork has signaled, such as via RRC, that the power control should begoverned by the serving radio base station and the difference in DL pathloss estimated with respect to the serving radio base station and thenon-serving radio base station indicates that the serving radio basestation has a weaker link, i.e. UL control channel, preferably HS-DPCCH,possibly accounting for an offset, which could be configured via RRCsignaling.

The present embodiments can in fact also be used in a situation wherethe quality of the UL control channel, preferably HS-DPCCH, isexcessive. In such a case, a quality representation is generated for theUL control channel as previously disclosed herein in connection withstep S1. This quality representation is then compared to a thresholdvalue in step S2. However, in this case the threshold value ispreferably different from the previously disclosed embodiments. Hence,the threshold value preferably indicates a threshold for a maximumdesirable quality for the UL control channel. Thus, if the presentchannel quality would indeed exceed the maximum desirable quality thenthe user equipment should take actions as disclosed herein. The userequipment advantageously generates the quality representation in thisembodiment according to any of the embodiments discussed in theforegoing in connection with FIG. 4 or 5. This quality representation isthen compared to the threshold value and if the quality representationexceeds the threshold value this indicates an excessive high quality ofthe UL control channel (or in an alternative embodiment if the qualityrepresentation is below the threshold value this indicates an excessivehigh quality). The selective processing of received TPC commands in stepS3 preferably involves neglecting a selected fraction of TPC UP commandsthat are intended to trigger an increase in transmit power of the ULcontrol channel, preferably HS-DPCCH. Thus, this embodiment is basicallythe opposite as previously disclosed herein. The discussion with regardto determining the selected fraction and how the neglect of TPC commandsin the foregoing can also be applied to the present embodiments.

FIG. 7 is a schematic block diagram of an embodiment of a user equipment300 according to an embodiment. The user equipment 300 can be any devicethat is configured to communicate with radio base stations in thecommunication network. The user equipment 300 could therefore be in theform of a mobile telephone, a computer, tablet, desktop, laptop ornotebook or notepad having equipment required for communication withinthe communication network.

The user equipment 300 comprises a transceiver (TRX) 340 that isemployed for communication, preferably wireless radio-basedcommunication, with radio base stations in the communication network. Inthe figure this transceiver 340 has been illustrated as a single unitcomprising both transmitter and receiver functionality. This should,however, merely be seen as an illustrative example. In alternativeembodiments, the user equipment 300 comprises a transmitter and areceiver or at least one transmitter and at least one receiver. Thetransceiver 340, or transmitter and receiver, is typically connected toan antenna (not illustrated), such as a common transmission andreception antenna or separate transmission and reception antennas.

According to the embodiments, the user equipment 300 comprises arepresentation generator 310 that is configured to generate a qualityrepresentation of an UL control channel, preferably HS-DPCCH, from theuser equipment 300 to its serving radio base station. This qualityrepresentation is employed by a comparator 320 that is configured tocompare the quality representation from the representation generator 310with a threshold value. The user equipment 300 further comprises aprocessor 330 configured to perform a selective processing of TPCcommands received by the transceiver 340 (or receiver) based on theoutcome of the comparison performed by the comparator 320. Thus, theprocessor 330 thereby determines how the received TPC commands should beused by the user equipment 300 based on whether the qualityrepresentation exceeds or is below the threshold value.

In a particular embodiment, the processor 330 is configured to neglect aselected fraction of the received TPC commands as determined based onthe comparison. Hence, in this case the processor 330 and thereby theuser equipment 300 will not perform any transmit power adjustment basedon the neglected TPC command(s).

The processor 330 is preferably configured, if the comparison indicatesthat the current quality of the UL control channel is poor, such as whenthe quality representation is below the threshold value, to neglect aselected fraction of TPC commands indicating a reduction in transmitpower and originating from a non-serving radio base station.

The processor 330 can perform the selective processing, i.e. determiningwhether to neglect a received TPC command or not, as previouslydisclosed herein, i.e. neglect every TPC DOWN command (or TPC UP commandin the case of excessive HS-DPCCH quality), neglect every second, third,etc. TPC command or determine which particular TPC command(s) to neglectbased on the quality representation generated by the representationgenerator 310.

In an embodiment, the processor 330 is configured to operate accordingtwo different processing modes. Firstly, if the comparison performed bythe comparator 320 indicates a poor quality of the UL control channel,the processor 330 neglects a selected fraction of the received TPC DOWNcommands as previously disclosed herein. Secondly, if the comparisonperformed by the comparator 320 instead indicates a sufficient qualityof the UL control channel, the processor 330 preferably does not neglectany received TPC commands but instead adjusts, i.e. increases ordecreases, the transmit power of the user equipment based on the TPCcommands.

In another embodiment, the processor 330 is configured to operateaccording three different processing modes. The two first suchprocessing modes are the ones described above. The third processing modeis used if the comparison performed by the comparator 320 indicates anexcessive quality of the UL control channel. The processor 330 thenneglects a selected fraction of the received TPC UP commands.

FIG. 8 is a schematic block diagram of an embodiment of therepresentation generator 310 in FIG. 7. In this embodiment, therepresentation generator 310 comprises a quality estimator 313configured to determine multiple quality estimates to the UL controlchannel, preferably HS-DPCCH, at different time instances. The qualityestimator 313 could then determine these quality estimates as previouslydisclosed herein, i.e. based on i) a comparison of transmitted HARQACK/NACK messages and received packet transmissions, ii) monitoring TPCcommands transmitted on F-DPCH from the serving radio base station, iii)an estimation of the difference in path loss to the serving radio basestation and the at least one other radio base station, or iv) acombination of any of i) to iii).

The representation generator 310 then comprises a calculator 314 that isconfigured to calculate the quality representation based on the multiplequality estimates determined by the quality estimator 313. In thisembodiment, the calculator 314 could calculate the qualityrepresentation based on an average of the multiple quality estimates oras a median of the multiple quality estimates.

FIG. 9 is a schematic block diagram of another embodiment of therepresentation generator 310 in FIG. 7. The representation generator 310comprises the previously described quality estimator 313. However, inthis embodiment the representation generator 310 comprises a selector315 that is configured to select a maximum quality estimate among themultiple quality estimates from the quality estimator 313 as the qualityrepresentation for the UL control channel. In an alternative embodiment,the selector 315 instead selects the minimum quality estimate as thequality representation in particular if the processor of the userequipment is configured to neglect TPC UP commands during a situationwith excessive quality of the UL control channel.

The embodiments of the representation generator 310 illustrated in FIGS.8 and 9 could alternative be implemented by arranging the qualityestimator 313 and the calculator 314 or the quality estimator 313 andthe selector 315 as separate units in the user equipment 300.

The units 310-340 of the user equipment 300 can be implemented inhardware, in software or a combination of hardware and software.Although the respective units 310-340 disclosed in conjunction with FIG.7 and units 313 and 314 in FIG. 8 and units 313 and 315 in FIG. 9 havebeen disclosed as physically separate units 310-340 in the userequipment 300, and all may be special purpose circuits, such as ASICs(Application Specific Integrated Circuits), alternative embodiments arepossible where some or all of the units 310-340 are implemented ascomputer program modules running on a general purpose processor.

In such a case and with reference to FIG. 10, the user equipment 300comprises a processing unit 70, such as a DSP (Digital Signal Processor)or CPU (Central Processing Unit). The processing unit 70 can be a singleunit or a plurality of units for performing different steps of themethod described herein. The user equipment 300 also comprises at leastone computer program product 60 in the form of a non-volatile memory,for instance an EEPROM (Electrically Erasable Programmable Read-OnlyMemory), a flash memory or a disk drive. The computer program product 60comprises a computer program 50, which comprises code means 51-53 whichwhen run on the user equipment 300, such as by the processing unit 70,causes the user equipment 300 to perform the steps of the methoddescribed in the foregoing in connection with FIG. 3. Hence, in anembodiment the code means 51-53 in the computer program 50 comprises arepresentation generating module 51 for generating a qualityrepresentation, a comparing module 52 for comparing the qualityrepresentation to a threshold value and a processing module 53 forperforming a selecting processing of TPC commands. These modules 51-53essentially perform the steps of the flow chart in FIG. 3 when run onthe processing unit 70. Thus, when the different modules 51-52 are runon the processing unit they correspond to the corresponding units310-330 of FIG. 7.

The computer program 50 may additionally comprise a quality estimatingmodule and a calculating module or a selecting module as disclosed inconnection with FIG. 8 or 9. The user equipment 300 also comprises atransceiver 80, or transmitter and receiver, or a general input andoutput (I/O) unit in order to enable communication with the radio basestations in the communication network.

The embodiments as disclosed herein can be used to achieve a certainDPCCH SIR quality at the serving radio base station for a user equipmentwhen in communication with multiple radio base stations, such as duringSHO. By ensuring such a sufficient DPCCH quality at the serving radiobase station also the HS-DPCCH can be decoded and therefore the downlinkHDSPA performance is not affected. By being able to provide sufficientHS-DPCCH quality the embodiments enable introduction of techniques, suchas multi-antenna transmission techniques for the uplink, complementingtraditional macro radio base stations with micro and/or pico radio basestations and per-HARQ scheduling for improving uplink orthogonality, incommunication networks.

A further advantage of the present embodiments where a user equipment iscapable of dynamically adapting the HS-DPCCH transmission power is thatthe adaptation can be performed in response to rapid quality changes,such as changes in effective path loss, e.g. due to fading. This shouldbe compared to an adaptation which is performed at the network side,such as in the RNC, which then typically is not as quick to respond toquality changes.

The embodiments described above are to be understood as a fewillustrative examples of the present invention. It will be understood bythose skilled in the art that various modifications, combinations andchanges may be made to the embodiments without departing from the scopeof the present invention. In particular, different part solutions in thedifferent embodiments can be combined in other configurations, wheretechnically possible. The scope of the present invention is, however,defined by the appended claims.

1-14. (canceled)
 15. A power control method implemented by a userequipment in a communication network when the user equipment is incommunication with a serving radio base station and at least one otherradio base station over a radio interface on uplink channels, the methodcomprising: generating a quality representation of an uplink controlchannel between the user equipment and the serving radio base station;comparing the quality representation to a threshold value; andperforming, based on the comparison of the quality representation to thethreshold value, a selective processing of transmit power controlcommands received from at least one of the serving radio base stationand the at least one other radio base station.
 16. The method accordingto claim 15, wherein generating the quality representation comprises:determining multiple quality estimates for the uplink control channel atdifferent time instances; and calculating the quality representationbased on an average of the multiple quality estimates.
 17. The methodaccording to claim 15, wherein generating the quality representationcomprises: determining multiple quality estimates for the uplink controlchannel at different time instances; and selecting a maximum qualityestimate among the multiple quality estimates as the qualityrepresentation.
 18. The method according to claim 15, wherein performingthe selective processing of transmit power control commands comprisesneglecting, based on the comparison of the quality representation to thethreshold value, a selected fraction of the transmit power controlcommands that are intended to trigger a decrease in transmit power ofthe uplink control channel.
 19. The method according to claim 18,further comprising determining the selected fraction of transmit powercontrol commands based on the quality representation.
 20. The methodaccording to claim 15, wherein generating the quality representationcomprises generating the quality representation of a high speeddedicated physical control channel (HS-DPCCH) between the user equipmentand the serving radio base station.
 21. A user equipment in acommunication network in communication with a serving radio base stationand at least one other radio base station over a radio interface onuplink channels, wherein the user equipment comprises: a representationgenerator configured to generate a quality representation of an uplinkcontrol channel between the user equipment and the serving radio basestation; a comparator configured to compare the quality representationto a threshold value; and a processor configured to perform, based onthe comparison of the quality representation to the threshold value, aselective processing of transmit power control commands received by areceiver of the user equipment from at least one of the serving radiobase station and the at least one other radio base station.
 22. The userequipment according to claim 21, wherein the representation generatorcomprises: a quality estimator configured to determine multiple qualityestimates for the uplink control channel at different time instances;and a calculator configured to calculate the quality representationbased on an average of the multiple quality estimates.
 23. The userequipment according to claim 21, wherein the representation generatorcomprises: a quality estimator configured to determine multiple qualityestimates for the uplink control channel at different time instances;and a selector configured to select a maximum quality estimate among themultiple quality estimates as the quality representation.
 24. The userequipment according to claim 21, wherein the processor is configured toperform the selective processing of the transmit power control commandsby neglecting, based on the comparison of the quality representation tothe threshold value, a selected fraction of the transmit power controlcommands that are intended to trigger a decrease in transmit power ofthe uplink control channel.
 25. The user equipment according to claim24, wherein the processor is further configured to determine theselected fraction of transmit power control commands based on thequality representation.
 26. The user equipment according to claim 21,wherein the representation generator is configured to generate thequality representation of a high speed dedicated physical controlchannel (HS-DPCCH) between the user equipment and the serving radio basestation.
 27. A computer program stored in a computer program product ora computer readable medium for power control in a communication networkwhen the user equipment is in communication with a serving radio basestation and at least one other radio base station over a radio interfaceon uplink channels, the computer program comprises non-transientcomputer program instructions which when run by a processing unit of theuser equipment causes the processing unit to: generate a qualityrepresentation of an uplink control channel between the user equipmentand the serving radio base station; compare the quality representationto a threshold value; and perform, based on the comparison of thequality representation to the threshold value, a selective processing oftransmit power control commands received from at least one of theserving radio base station and the at least one other radio basestation.